XEAR NEW HARMONY, INDIANA. 9 



of the track of a tornado ; suppose tlie track to be one mile wide. Let H be 

 a tree standing near the left margin ; let A represent the bottom of the ascending 

 column, and the radii the afflux of air to the focal area ; let this focal area have a 

 progressive motion from A to G, at the rate of one mile per minute. When the 

 centre of the tornado is at A, it will be about four miles distant from //; conse- 

 quently 5^ will receive the wind in the direction from A; in one and a half minutes 

 the centre Avill have advanced to B, and 11 WAX receive the wind from h; as the 

 tornado approaches, the force of the wind increases, and in another minute and a 

 half the centre will have reached C, and 5^ will receive the wind from c; in the 

 next minute the centre will reach D, the wind will have reached its maximum 

 force, i?will receive the wind from d ; the wind in the last minute having veered, 

 with increasing rapidity, sixty degrees ; this is continued for another minute, until 

 the centre reaches E, when 5" will have the wind from e ; in the last one and a half 

 minutes the wind has veered, with maximum velocity, from N. E. to N. W. ; and, 

 during this rapid change, and greatly increased velocity, is it unlikely that, as the 

 tree is successively swayed round, the force of the wind should at this moment be 

 such as to prostrate the tree directly outwards, with the top of the stem at right 

 angles to the centre of the path ? This I think highly probable; and the prostrated 

 trees show, more or less, that where they had the power to withstand the first 

 impulse of the wind, they have been successively swayed round ; this mode of action 

 may be traced from one margin of the track to the other. Figs. 7, 8, 9, of the 

 map, are illustrative of these points. Fig. 7 is a view near the north margin of 

 the track, adjoining the S. "W. corner of Mr. Schuee's fence, looking east; the trees 

 are prostrated nearly due north, and exhibit the appearance of being suddenly 

 twisted, and thrown outwards from the centre of the path, as described. 



Fig. 8 is a sketch near the centre of the track, looking S. W. ; here is a tree pros- 

 trated from the N. W., interlocked in the forks of one prostrated from the S. E., 

 with three trees lying between them from the S. W., most clearly evidencing the 

 simultaneous overthrow from opposite points. The tree in the front, in a northerly 

 direction, and the illustration in Fig. 9, are further examples of the swaying round 

 and twisting of trees. It is taken from near the centre of the track. 



Another illustration in favor of the hypothesis of an ascending column, may be 

 drawn, I think, from the barometrical observations made at New Harmony. It 

 will be observed that the barometer fell half an inch from April 27 to the day of 

 the storm, April 30. This fall was so gentle that it did not on any of those days 

 mask the 9 A. M. maximum horary oscillation, and it may therefore be inferred 

 that the disturbing cause was distant. At 3 P. M., on the day of the storm, one 

 hour and a half previous to the tornado passing the meridian of New Harmony, 

 the height of the mercury in the barometer was 29.090 inches ; at 4.30 P. M., at the 

 time of the passage of the tornado, it was 29.170; and at G P. M., one hour and a 

 half after the passage, it was 29.090. This sudden rise and fiill of 0.80 of an inch 

 at the time, which is usually that of the minimum horary oscillation, is remark- 

 able, and we may attribute it to the local action of the tornado, and account for it 

 by Espy's hypothesis, as explained in the following paragraph. 



